1. Field of the Invention
This invention generally relates to a hammermill and, particularly to a heavy duty hammer assembly for a hammermill of the type used to break up discarded automobile bodies.
2. Description of the Prior Art
Hammermills of the type contemplated herein are widely used to reduce large metal objects, such as cars, into small metal fragments by the rotation of a hammermill assembly within the housing of the hammermill. Hammermills of this general type are shown in U.S. Letters Pat. No. 4,222,530 issued Sept. 16, 1980, entitled "Replaceable Protective Means For End Disk of Shredder" and assigned to the same assignee. The assembly disclosed in this patent is formed by a plurality of 3 arm spiders which are alternately off set and axially aligned on the shaft in the hammermill housing. A hammer can then be mounted between the arms of every other spider with sufficient space to allow the hammers to rotate freely on the spider arms.
These hammermills are being used to shread heavy metal scrap commonly denominated #2 scrap which has resulted in an increase in down time due to repair and replacement of over stressed parts. The hammer assembly generally includes thirteen three arm spiders mounted on the drive shaft with an end plate at each end of the spiders. The drive shaft is provided with bearing sleeves at each end and key ways on diametrically opposite sides of the drive shaft. Each alternate spider requiring a key on the opposite side of the shaft to properly align the arms of the spiders in six rows. With this arrangement up to thirty-nine hammers could be mounted on the spider arms however only ten to twenty-four hammers are normally used.
The spider arms on each spider are spaced 120.degree. apart around a hub portion that has a diameter corresponding to the diameter of a circle passing through the axis of the tie rod holes in the spiders. The spider arms extend radially outwardly from the hub portion a radial distance approximately twice the radius of the axis circle of the tie rod holes. With this arrangement stress areas have been noted in the spider arms when shredding heavy scrap which have caused cracking at the outer ends of the arms as well as at the intersection of the spider arms with the hub.